Object information obtaining device, display method, and non-transitory computer-readable storage medium

ABSTRACT

An object information obtaining device includes a light source which emits light, an acoustic wave detecting unit which detects a photoacoustic wave generated by irradiation of an object with the light, and outputs an electric signal in response to detection of the photoacoustic wave, and a processing unit configured to perform two or more types of processing to photoacoustic signal data based on the electric signal to obtain object information corresponding to each of the two or more types of processing, and to display on a display unit the object information corresponding to at least one processing selected by a user out of the two or more types of processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/700,996, filed Sep. 11, 2017, which is a Continuation of U.S. patentapplication Ser. No. 14/134,957, filed Dec. 19, 2013, which claimsforeign priority benefit of Japanese Patent Application No. 2012-286685,filed Dec. 28, 2012, all of which are hereby incorporated by referenceherein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to technology to obtain object informationbased on a photoacoustic wave generated by irradiation of light to anobject.

Description of the Related Art

Photo acoustic imaging (PAI) in an optical imaging technique developedbased on the photoacoustic effect. In photo acoustic imaging, forexample, an object such as a living body is irradiated with pulsed lightand a light absorber such as a blood vessel absorbs energy of the pulsedlight to generate a photoacoustic wave. An acoustic wave detecting unitdetects the photoacoustic wave generated by the photoacoustic effect.Then, a detection signal output from the acoustic wave detecting unit isanalyzed by image processing, for example, and object information isobtained.

As an example of photo acoustic imaging, Non-Patent Document 1 entitled“Universal back-projection algorithm for photoacoustic computedtomography”, disclosed by Xu et al., PHYSICAL REVIEW E 71,016706 (2005),discloses obtaining initial sound pressure distribution as the objectinformation by applying universal back-projection reconstructionprocessing (hereinafter, referred to as “UBP processing”) to thedetection signal of the photoacoustic wave.

SUMMARY OF THE INVENTION

An object information obtaining device disclosed in this specificationis provided with a light source configured to emit light, an acousticwave detecting unit configured to detect a photoacoustic wave generatedby irradiation of an object with the light, and to output an electricsignal in response to detection of the acoustic wave, and a processingunit configured to perform two or more types of processing tophotoacoustic signal data based on the electric signal to obtain objectinformation corresponding to each of the two or more types ofprocessing, and to display on a display unit the object informationcorresponding to at least one processing selected by a user out of thetwo or more types of processing. Further features of the presentinvention will become apparent from the following description ofexemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an object information obtaining deviceaccording to this embodiment.

FIG. 2 is a view illustrating a processing unit according to thisembodiment in detail.

FIG. 3 is a view illustrating a flow of a method of obtaining objectinformation according to this embodiment.

FIG. 4A is a view illustrating a simulation model according to thisembodiment.

FIG. 4B is a view illustrating a simulation result of a Fourier domainreconstruction processing according to this embodiment.

FIG. 4C is a view illustrating a simulation result of a time domainreconstruction processing according to this embodiment.

FIG. 4D is a view illustrating a simulation result of a model basereconstruction processing according to this embodiment.

FIG. 5 is a view illustrating a flow of a method of obtaining objectinformation according to Example 1 of the present invention.

FIG. 6 is a view illustrating a processing unit according to Example 1of the present invention in detail.

FIG. 7 is a view illustrating a screen displayed on a display accordingto Example 1 of the present invention.

FIG. 8 is a view illustrating a flow of a method of obtaining objectinformation according to Example 2 of the present invention.

FIG. 9 is a view illustrating a screen displayed on a display accordingto Example 2 of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Object information according to one embodiment includes initial soundpressure of a photoacoustic wave generated by a photoacoustic effect,optical energy absorption density derived from the initial soundpressure, an absorption coefficient, density of a substance formingtissue and the like. Herein, density of a substance may be determined bylevels of oxygen saturation, oxyhemoglobin density, deoxyhemoglobindensity, total hemoglobin density and the like. The total hemoglobindensity is a sum of the oxyhemoglobin density and the deoxyhemoglobindensity.

The object information in this embodiment may be not numerical data butdistribution information of each position in an object. That is to say,the distribution information such as absorption coefficient distributionand oxygen saturation distribution may be used as the objectinformation.

Further improvement in method of displaying the object informationobtained only by specific processing (UBP reconstruction processing) asdisclosed in Non-Patent Document 1 is desired from a diagnosticviewpoint.

For example, a real image corresponding to the object might be displayedin a different manner depending on a type of the processing. Therefore,usefulness in diagnosis of an observation object might be differentdepending on the type of the processing.

A virtual image referred to as an artifact might be present in adiagnostic image obtained through the reconstruction processing. Theartifact might preclude appropriate diagnosis. As it is known, dependingon the type of the reconstruction processing, artifacts appeardifferently in a reconstructed image.

Therefore, display of object information obtained by the specificprocessing alone might be insufficient at the time of diagnosis.

In accordance with at least one embodiment of the present invention, atleast one processing is selected by a user from two or more types ofprocessing to photoacoustic signal data (also referred to as raw data).According to this, the user may confirm the object information obtainedby desired processing, so that the user may selectively use the imagecorresponding to the processing determined to be useful according to asymptom in the diagnosis.

With the object information obtaining device capable of executing onlyone specific processing, there is a case in which processing requiringlong processing time should be executed even though the user wants tosee a diagnostic result in a short time. With the object informationobtaining device capable of executing only the specific processing,there also is a case in which processing based on a simple model shouldbe executed even though the user wants to observe detailed informationeven if it takes long processing time.

Therefore, according to an embodiment disclosed herein, the user mayalso select the desired processing in consideration of acceptableprocessing time to the user. That is to say, according to thisembodiment, the user may select the object information corresponding tothe desired processing determined by the user to be highly useful withinthe acceptable processing time to the user.

The present embodiment is hereinafter described with reference to thedrawings. In the drawings, the same reference sign is assigned to thesame component, and the description thereof is not repeated.

A basic configuration of the object information obtaining device(information obtaining apparatus) according to this embodimentillustrated in FIG. 1 is first described.

The object information obtaining device illustrated in FIG. 1 includes alight source 110, an optical system 120, an acoustic wave detecting unit130, a processing unit 140 as a computer, an input unit 150, and adisplay unit 160 in order to obtain information of a living body 100 asthe object.

FIG. 2 is a block diagram illustrating relevant parts of a computer,which is an example of a data processing apparatus including theprocessing unit 140 and peripheral elements of the processing unit 140.As illustrated in FIG. 2, the processing unit 140 is provided with anarithmetic unit 141 and a storage unit 142. An example of the processingunit 140 includes, but is not limited to, a microprocessor chip, such asa CPU (central processing unit) or MPU (micro processing unit). Anexample of storage unit 140 includes, but is not limited to, RAM or ROMmemory.

The arithmetic unit 141 controls operation of each component forming theobject information obtaining device through a data network 200. Thearithmetic unit 141 reads a program in which processing steps for (amethod of) obtaining object information to be described later is savedin the storage unit 142 and allows the object information obtainingdevice to execute the method of obtaining object information.

Each component of the object information obtaining device according tothis embodiment is hereinafter described in detail.

(Light Source 110)

The light source 110 is preferably a pulse light source capable ofemitting light pulses lasting a few nanoseconds to few microseconds.Specifically, the light source 110 is preferably capable of emittinglight having a pulse width of approximately 10 nanoseconds in order toefficiently generate the photoacoustic wave. A wavelength of the lightwhich can be emitted by the light source 110 is desirably the wavelengthat which the light propagates into the object. Specifically, when theobject is a living body, such as a human or animal body, a preferablewavelength is not shorter than 500 nm and not longer than 1500 nm.

A laser or a light-emitting diode are examples of a light source thatmay be used in some embodiments disclosed herein. As the laser, variouslasers such as a solid-state laser, a gas laser, a dye laser, and asemiconductor laser may be used. For example, the laser used in thisembodiment includes an alexandrite laser, an yttrium-aluminum-garnetlaser, a titanium-sapphire laser and the like.

(Optical System 120)

The light emitted from the light source 110 is typically guided to theliving body 100 while being shaped into a desired light distributionshape by means of an optical component such as a lens and a mirror. Inaddition, it is also possible to propagate the pulsed light by using awaveguide or an optical fiber. The optical component used to shape thelight distribution includes, for example, a mirror reflecting the light,a lens collecting and magnifying the light or changing a focusing shapethereof, a prism dispersing, refracting, and reflecting the light, theoptical fiber propagating the light, a diffusion plate dispersing thelight and other like optical components or combinations thereof. Anytype or number of such optical components may be used as long as theobject is irradiated with the light emitted from the light source 110 inthe desired manner.

However, when the light emitted by the light source 110 may be guideddirectly to the object as desired light, it may not be necessary to usethe optical system 120.

(Acoustic Wave Detecting Unit 130)

The acoustic wave detecting unit 130 is provided with one or moreopto-acoustic transducers and a housing enclosing the transducer(s). Anopto-acoustic transducer, as used herein, is an element capable ofdetecting an acoustic wave.

The transducer receives the acoustic wave such as the photoacoustic waveand an ultrasonic echo to transform it to an electric signal being ananalog signal. Any transducer may be used as long as the transducer isconfigured to receive the acoustic wave. Examples of transducer includea transducer using a piezoelectric phenomenon, a transducer usingoptical resonance, a transducer using change in capacitance, and otherlike transducers. The acoustic wave detecting unit 130 is preferablyprovided with a plurality of transducers arranged in an array.

(Processing Unit 140)

The processing unit 140 is provided with the arithmetic unit 141 and thestorage unit 142 as illustrated in FIG. 2.

The arithmetic unit 141 is typically formed of an arithmetic elementsuch as a CPU, a GPU, an A/D converter, a FPGA (field programmable gatearray) card, and an ASIC (application specific integrated circuit) chip.Meanwhile, the arithmetic unit 141 may be formed not only of onearithmetic element but also of a plurality of arithmetic elements. Anyarithmetic element may be used to perform the disclosed process.

The storage unit 142 is typically formed of a storage medium such as aROM memory, a RAM memory, a hard disk drive, or a combination thereof.That is, the storage unit 142 may be formed not only of one storagemedium but also of a plurality of storage media.

The arithmetic unit 141 may make a gain adjustment to increase ordecrease an amplification gain according to time that elapses fromirradiation of the light to arrival of the acoustic wave at the elementof the acoustic wave detecting unit 130 in order to obtain the imagehaving a uniform contrast regardless of a depth in the living body.

The arithmetic unit 141 may control light emission timing of the pulsedlight emitted from the light source 110, and may also control operationstart timing of the acoustic wave detecting unit 130 by using the pulsedlight as a trigger signal. The arithmetic unit 141 may control displayoperations of the display unit 160.

The arithmetic unit 141 is preferably configured to simultaneouslyperform pipeline processing of a plurality of signals when a pluralityof detecting signals is obtained from the acoustic wave detecting unit130. According to this, time that elapses before the object informationis obtained may be shortened.

Preferably, each processing operation performed by the processing unit140 may be saved in the storage unit 142 as part of the program to beexecuted by the arithmetic unit 141. The storage unit 142 in which theprogram is saved is a non-transitory computer-readable recording medium.

The processing unit 140 and the acoustic wave detecting unit 130 may beprovided as an integrated unit. Then, the processing unit provided onthe acoustic wave detecting unit may perform a part of signalprocessing, and the processing unit provided outside the acoustic wavedetecting unit may perform the remainder of signal processing. In thiscase, the processing unit provided on the acoustic wave detecting unitand the processing unit provided outside the acoustic wave detectingunit may be collectively referred to as the processing unit according tothis embodiment.

(Input Unit 150)

The input unit 150 is a user interface (I/F) configured to accept anoperation (e.g., input) by the user. Information input by the user isinput from the input unit 150 to the processing unit 140.

For example, a pointing device such as a mouse and a keyboard, agraphics tablet type and the like may be adapted as the input unit 150.A mechanical device such as a button and a dial provided on a deviceforming the object information obtaining device, or other I/F device mayalso be adapted as the input unit 150. When a touch panel display isused as the display unit 160, the display unit 160 may also be adaptedto function as the input unit 150.

Naturally, the input unit 150 may be provided as a user I/F disposedseparately from the object information obtaining device and connectedthereto via the data network 200.

(Display Unit 160)

The display unit 160 is a device which displays the object informationoutput from the processing unit 140.

Although a liquid crystal display (LCD) and the like is typically usedas the display unit 160, another type of display such as a plasmadisplay, an organic EL display, and a FED may also be used. It is alsopossible to integrally form the input unit 150 and the display unit 160by adopting the touch panel display as the display unit 160.

The display unit 160 may also be provided separately from the objectinformation obtaining device according to this embodiment.

Next, the method of obtaining object information according to thisembodiment using the object information obtaining device illustrated inFIGS. 1 and 2 is described with reference to a flow illustrated in FIG.3. The flow process illustrated in FIG. 3 is example of an algorithmexecuted by the processing unit 140.

(S301: Step of Obtaining Photoacoustic Signal Data)

At step S301, the light emitted by the light source 110 is applied tothe living body 100 as pulse light 121 through the optical system 120.Then, a light absorber 101 absorbs the pulse light 121 and aphotoacoustic wave 102 is generated by the photoacoustic effect.

Next, the acoustic wave detecting unit 130 transforms the photoacousticwave 102 to the electric signal being the analog signal to output to theprocessing unit 140. The arithmetic unit 141 saves the electric signaloutput from the acoustic wave detecting unit 130 in the storage unit 142as the photoacoustic signal data.

In this embodiment, data obtained when the electric signal output fromthe acoustic wave detecting unit 130 is saved in the storage unit 142 ismade into the photoacoustic signal data. The photoacoustic signal datamay be read from the storage unit 142 by the arithmetic unit 141 to beused in the two or more types of processing to be described later.

The electric signal output from the acoustic wave detecting unit 130 istypically amplified and subjected to the A/D conversion to be saved inthe storage unit 142 as the photoacoustic signal data. The electricsignal output from the acoustic wave detecting unit 130 may also besaved in the storage unit 142 as the photoacoustic signal data afterbeing averaged.

The photoacoustic signal data is saved in the storage unit 142 in thismanner. The arithmetic unit 141 may use the photoacoustic signal dataincluding the same photoacoustic signal data corresponding to thephotoacoustic wave detected at certain time in a plurality of types ofprocessing to be described later.

In photo acoustic imaging, it is possible to apply different types ofprocessing to the photoacoustic signal data including the samephotoacoustic signal data obtained by detecting the photoacoustic waveat certain time. According to this, the object information at the sametime corresponding to each of the different types of processing may beobtained.

That is, the object information corresponding to the desired processingout of pieces of object information at the same time obtained byapplying each of the two or more types of processing to thephotoacoustic signal data including the same data may be selectivelydisplayed.

The arithmetic unit 141 may also obtain the object informationcorresponding to each processing by performing the two or more types ofprocessing to the photoacoustic signal data not including the same data.

(S302: Step of Selecting Information of Desired Processing from Two orMore Types of Processing)

At step S302, the user selects the desired processing from two or moretypes of processing by using the input unit 150. Then, the input unit150 outputs the information of the processing selected by the user tothe processing unit 140. At that time, the information of the selectedprocessing is saved in the storage unit 142.

An example of the input unit 150 for the user to select the desiredprocessing from the two or more types of processing is hereinafterdescribed. That is, an example of a method of inputting the informationof the desired processing by the user is described.

For example, the user may select the desired processing by pressing amechanical button as the input unit 150 corresponding to each of the twoor more types of processing. Alternatively, the user may select thedesired processing by turning a mechanical dial as the input unit 150corresponding to each of the two or more types of processing.

As another example, the user may also select the desired processing byselecting an item indicating the processing displayed on the displayunit 160 by means of a pointing device (mouse), the keyboard and thelike as the input unit 150. At that time, the display unit 160 maydisplay the items indicating the processing next to one another as iconsor display them as a menu. The item related to the processing displayedon the display unit 160 may be always displayed beside the image of theobject information or may be configured to be displayed when the userperforms some operation by using the input unit 150. For example, thedisplay unit 160 may be configured such that the item indicating theprocessing is displayed on the display unit 160 by a click of themechanical button provided on the mouse as the input unit 150.

The method is not limited to the above-described method and any methodmay be adopted as long as the user may select the desired processing outof the two or more types of processing.

The object information obtaining device is preferably configured suchthat progress of each processing is visually presented to the user. Forexample, it is possible to configure the object information obtainingdevice such that the progress of each processing is visually presentedby displaying a progress bar or displaying a predicted calculationtermination time on the display unit 160. In addition, it is alsopossible to use a circular progress mark in which an angle of a partwith changed color changes as the processing advances. Alternatively, acolor of the item corresponding to the processing may be changedaccording to a progress status such as completion of the processing orthe progress status may be displayed in characters in the vicinity ofthe item.

The object information obtaining device according to this embodiment ispreferably configured such that the progress of the processing may begrasped and the user may optionally stop the processing currently beingcalculated. Such configuration allows the user to start a differentprocess operation when the user sees the progress bar and determinesthat the progress of the processing currently being calculated is notconvenient (e.g., the processing is taking too long, the processing isnot good due to a processing error, the type of processing was chosen inerror, etc.).

Image reconstruction processing selected by default may be set inadvance in a file in the storage unit 142. In this case, the arithmeticunit 141 may read default processing at the beginning of step S302 andexecute the processing selected by default if the user does notespecially select other processing. It is also possible that the usermay intentionally select the processing set by default.

The desired processing selected by the user may be at least one type ofprocessing. In this embodiment, at least two types of processing may beselected from three or more types of processing. At that time, theobject information obtaining device according to this embodiment may beconfigured such that a plurality of combinations of at least two typesof processing may be selected. According to this, the user may selectthe desired processing with a high degree of freedom and it becomespossible to display the object information useful in the diagnosis.

(S303: Step of Obtaining Object Information by Performing DesiredProcessing)

At step S303, the arithmetic unit 141 obtains the object information byperforming the desired processing selected at S200 based on thephotoacoustic signal data saved in the storage unit 142. Herein, theobject information obtained by performing the desired processing isreferred to as “object information corresponding to the desiredprocessing”.

Meanwhile, the arithmetic unit 141 may read the program in which analgorithm of the processing is described stored in the storage unit 142and apply this processing to the photoacoustic signal data to obtain theobject information.

In this embodiment, three-dimensional voxel data and two-dimensionalpixel data as the object information may be obtained by the processing.

Herein, the processing according to this embodiment is intended to meanevery processing performed during transform from the photoacousticsignal data to the object information having a pathological value. Forexample, the processing according to this embodiment includes signalprocessing such as probe response correction processing and noiseremoval processing to generate different photoacoustic signal data basedon the photoacoustic signal data stored in the storage unit 142. Therealso is, for example, reconstruction processing such as time domainreconstruction processing, Fourier domain reconstruction processing, andmodel base reconstruction processing to generate the object informationfrom the photoacoustic signal data stored in the storage unit 142 as theprocessing according to this embodiment. For example, the processingaccording to this embodiment includes image processing such asresolution improvement processing to generate different objectinformation based on the object information generated by theabove-described reconstruction processing.

An example of each processing is hereinafter described.

The probe response correction processing (hereinafter, referred to as“BD processing”) as the signal processing according to this embodimentis the processing to correct signal deterioration due to band limitationof a probe by applying processing based on a blind deconvolutionalgorithm to the photoacoustic signal data (refer to Patent Document 1(Japanese Patent Application Laid-Open No. 2012-135462)). When thephotoacoustic wave is transformed to the electric signal by the acousticwave detecting unit 130, there is limitation in receiving bandwidth ofthe acoustic wave detecting unit 130, so that a waveform of the electricsignal might change to generate ringing. This ringing causes theartifact appearing in the vicinity of the light absorber on the image todeteriorate resolution. Probe response correction has an effect ofdecreasing the ringing by the acoustic wave detecting unit, therebydecreasing the artifact and improving the resolution.

The noise removal processing (hereinafter, referred to as “waveletprocessing”) as the signal processing according to this embodiment isthe processing to remove a noise component of the photoacoustic signaldata through basis pursuit by a wavelet function of the photoacousticsignal data. A waveform of the signal resulting from the photoacousticwave is known to be an N-shaped waveform under an ideal condition (referto Non-Patent Document 2 (Sergey A. Ermilov, RedaGharieb, AndreConjusteau, Tom Miller, Ketan Mehta, and Alexander A. Oraevsky, “DataProcessing and quasi-3D optoacoustic imaging of tumors in the breastusing a linear arc-shaped array of ultrasonic transducers”, Proc. ofSPIE, Vol. 6856). On the other hand, random noise being an irregularwaveform mixed from an electric system and the like of the device issuperimposed on the signal resulting from the photoacoustic wave.Therefore, the signal resulting from the noise is discriminated from thesignal resulting from the photoacoustic wave by applying a discretewavelet transform to the photoacoustic signal data and removing acoefficient having a small absolute value from a result thereof. Thewavelet processing has a large effect when the signal resulting from thephoto acoustic wave has the waveform close to the ideal waveform. On theother hand, when a frequency of the photoacoustic wave is significantlydifferent from a bandwidth of the acoustic wave detecting unit, when thenoise is too large, and when a plurality of waveforms are superimposeddue to a feature of the object, there is a case in which an effect ofimproving an image quality by the wavelet processing is small.

The time domain reconstruction processing (hereinafter, referred to as“TD processing”) as the reconstruction processing is the processing toestimate a sonic wave source by superimposing sonic wave signals in areal space by using a property that the photoacoustic wave is aspherical wave to generate the voxel data (refer to Patent Document 2(Japanese Patent Application Laid-Open No. 2010-35806)). The TDprocessing specifically includes UBP processing disclosed in Non-PatentDocument 1. The TD processing is performed in the real space, so that aneffect of a measurement system is easily introduced as compared to theFourier domain reconstruction processing and the like to be describedlater. For example, it is possible to decrease a side-lobe artifact byapplying weighted correction processing of a solid angle and the like inconsideration of a state of the acoustic wave detecting unit 130, forexample.

The Fourier domain reconstruction processing (hereinafter, referred toas “FD processing”) as the reconstruction processing is the processingto estimate the sonic wave source by superimposing the detection signalsin a frequency domain by using a Fourier transform and an inverseFourier transform to generate the voxel data (refer to Japanese PatentApplication Laid-Open No. 2010-35806). The processing may be performedin a short time by using a fast Fourier transform. However, the effectof the measurement system is not easily introduced in a frequency spaceas compared to the real space. Therefore, it is difficult to apply theweighted correction processing of the solid angle and the like inconsideration of the state of the acoustic wave detecting unit which maybe performed in the TD processing, for example, and there is a case inwhich the side-lobe artifact is generated.

The model base reconstruction processing (hereinafter, referred to as“MBP processing”) as the reconstruction processing is the processing toestimate the sonic wave source such that difference between acalculation result based on a propagation model of an idealphotoacoustic wave and the photoacoustic signal data is minimum togenerate the voxel data (refer to Patent Document 3 (Japanese PatentApplication Laid-Open No. 2011-143175)). By using a descriptive model ofa phenomenon, the measurement system may be more strictly described thanin the TD processing and the FD processing. According to this, an imagewith few artifacts may be obtained. However, since it is required torepetitively calculate such that the difference between thephotoacoustic signal data and the calculation result is minimum in theMBP processing, longer processing time than that in the TD processingand the FD processing is typically required. It is difficult to reflectall the phenomena in the model, and when a generated phenomenon cannotbe reflected in the model, there is a case in which quantitativeness ofthe object information obtained by the MBP processing is deteriorated.

The resolution improvement processing (hereinafter, referred to as “CFprocessing”) as the image processing is the processing to reduce theartifact generated by limitation of a viewing angle of the probe byusing a coherent filter in the object information obtained by theabove-described reconstruction processing (refer to Patent Document 4(Japanese Patent Application Laid-Open No. 2011-120765). According tothis, a high-resolution image of the object information may be obtained.This is the processing to calculate a coefficient which is set to 1 whenphase signals of the photoacoustic wave are in phase and set to 0 whenthey are out of phase for each voxel and multiply distribution of thecoefficients by the image. The CF processing is especially effectivewhen sound speed distribution of the object is nearly constant. On theother hand, when variation in the sound speed distribution of the objectis large, an effect of improving the image quality by the CF processingmight be small.

Hereinafter, a result obtained when various types of reconstructionprocessing are applied to the photoacoustic signal data obtained bysimulating step S301 using a model having absorption coefficientdistribution illustrated in FIG. 4A is described. Herein, an x-axiscorresponds to a horizontal direction and a z-axis corresponds to avertical direction in FIG. 4A. Herein, a case in which a one-dimensionaltransducer array in an x-axis direction is arranged on a lowest part inFIG. 4A and the one-dimensional transducer array detects thephotoacoustic wave propagated from an upper side of the z-axis issimulated.

FIG. 4B illustrates initial sound pressure distribution when the FDprocessing is performed. FIG. 4C illustrates the initial sound pressuredistribution when the TD processing is performed. FIG. 4D illustratesthe initial sound pressure distribution when the MBP processing isperformed.

As is understood from the images in FIGS. 4B to 4D, different images areobtained for the same absorption coefficient distribution depending onthe type of the processing.

For example, in the image obtained by the FD processing illustrated inFIG. 4B, an arc-like artifact is confirmed. In the image obtained by theTD processing illustrated in FIG. 4C, the artifact extending in thex-axis direction is confirmed. It is understood that the artifact in theimage obtained by the MBP processing illustrated in FIG. 4D is entirelysuppressed as compared to the artifact in the images illustrated inFIGS. 4B and 4C.

In the images illustrated in FIGS. 4B and 4C, it is understood thatconnection of the initial sound pressure distribution corresponding tothe absorption coefficient distribution extending in a z-axis directiondecreases as compared to that in the image illustrated in FIG. 4D.

As described above, appropriate processing differs according to ameasurement environment and a site wanted to be observed. Time requiredfor the processing differs depending on the type of processing.

(S304: Step of Displaying Object Information Corresponding to DesiredProcessing)

At this step, the arithmetic unit 141 calculates display data to bedisplayed on the display unit 160 based on the voxel data (or the pixeldata) of the object information saved in the storage unit 142 to displaythe display data on the display unit 160.

Meanwhile, the display data of desired dimension out of one dimension,two dimensions, and three dimensions may be obtained from the voxel data(or the pixel data). The object information obtaining device may beconfigured such that the user may set the dimension of the display databy using the input unit 150.

As described above, in the object information obtaining device accordingto this embodiment, it is possible to display the object informationcorresponding to the desired processing selected by the user out of thetwo or more types of processing on the display unit. According to this,it is possible to diagnose by using the image meeting needs of the usersuch as the processing time and the image quality from the images at thesame time obtained by each image reconstruction.

The configuration in which the object information corresponding to thedesired processing is obtained after the information of the desiredprocessing is obtained is described above. However, the objectinformation obtaining device according to this embodiment may also beconfigured such that the information of the desired processing isobtained and the object information corresponding to the information ofthe desired processing is displayed in a state in which the objectinformation corresponding to the desired processing is obtained inadvance. That is to say, step S302 may be executed after step S303 isexecuted and step S304 may be executed thereafter.

In this case, the image itself obtained after the processing is appliedto the photoacoustic signal data may be adopted as the item indicatingthe processing. That is to say, the user may select the processing byselecting the image. For example, it is possible that the images whoseprocessing is finished are sequentially displayed on the display unit160 and when the user selects one of a plurality of images, the image isdisplayed in an enlarged manner. By this method, the user may compareresults of a plurality of types of processing and may select the desiredimage even when the user does not have knowledge of the processing.

In this case, the object information obtaining device is preferablyconfigured such that the user cannot select the processing not finishedyet.

In this case, the object information obtaining device is preferablyfurther provided with notifying means of notifying the user of whetherthe processing is finished processing. Further, the notifying means ispreferably configured such that the user may visually recognize whetherthe processing is the finished processing.

For example, when the item indicating the object information isdisplayed on the display unit 160, it is possible to display the item ofthe finished processing and the item of the processing not finished yetin different colors and the like as the notifying means.

It is also possible to provide a lamp as the notifying meanscorresponding to each processing on the device forming the objectinformation obtaining device or another device. In this case, it ispossible to notify the user of whether the processing is the finishedprocessing by setting such that the lamp corresponding the finishedprocessing is turned on, for example.

It is also possible that the information of the desired processing isobtained and the object information corresponding to the desiredprocessing is displayed on the display unit 160 in a state in which theobject information different from the object information correspondingto the desired processing is displayed on the display unit 160. At thattime, the object information corresponding to the desired processing maybe displayed so as to be superimposed on the object informationdisplayed in advance or may be displayed next to the same. It is alsopossible to switch from the object information displayed in advance tothe object information corresponding to the desired processing todisplay on the display unit 160. That is to say, it is possible to hidethe object information displayed in advance from the display unit 160and display the object information corresponding to the desiredprocessing in an area on the display unit 160 in which the objectinformation is displayed. The display method may be set in advancebefore shipping or may be set by the user by means of the input unit150.

In this manner, the user may grasp pathological information which may begrasped from the object information displayed in advance and thepathological information which may grasped from the object informationcorresponding to the desired processing to diagnose in a comprehensivemanner. It is also possible to diagnose in a comprehensive manner bygrasping a plurality of pieces of pathological information without atime interval.

Example 1

Example 1 according to the present invention is subsequently describedwith reference to FIGS. 1, 5, and 6. FIG. 5 is a flow diagram of amethod of obtaining object information according to this example. FIG. 6is a schematic diagram illustrating a computer 140 as a processing unitaccording to this example in detail and a peripheral device. Asillustrated in FIG. 6, the computer 140 is provided with a CPU 641, aFPGA 642, and a GPU 643 as an arithmetic unit, and a ROM 644 and a RAM645 as a storage unit. Herein, the ROM 644 is used as a non-transitorycomputer-readable recording medium.

In this example, the CPU 641 controls operation of each componentforming an object information obtaining device through a data network200, which is similar to that shown in FIG. 2. The CPU 641 reads aprogram in which the method of obtaining object information according tothis example is described saved in the ROM 644 to allow the objectinformation obtaining device to execute the method of obtaining objectinformation. That is to say, the computer 140 executes a flowillustrated in FIG. 5.

At step S501, a user operated an input unit 150 to input a measurementparameter. The measurement parameter was saved in the RAM 645 as thestorage unit. At this step, the user set a wavelength of laser lightused in measurement and the number of irradiation times of the laserlight to a breast 100 of a subject as an object in one measurement asthe measurement parameters. Meanwhile, in this example, the user set thewavelength of the laser light used in the measurement to 797 nm and thenumber of irradiation times of the laser light to 30.

Subsequently, at step S502, the CPU 641 issues an instruction based onthe measurement parameter to a titanium-sapphire laser 110 as a lightsource to allow the same to emit the laser light. The laser light wasapplied to the breast 100 as pulse light 121 with a pulse width of 50 nmthrough an optical fiber 120. Then, the breast 100 absorbed the pulselight 121 and a photoacoustic wave reflecting absorption coefficientdistribution in the breast 100 was generated. Meanwhile, thetitan-sapphire laser 110 in this example includes a flash lamp and aQ-switch as means of exciting an internal laser medium and lightemission timing was controlled by the instruction from the CPU 641.

Subsequently, at step S503, a CMUT array 130 as an acoustic wavedetecting unit transformed the photoacoustic wave to an electric signaland output the electric signal to the processing unit 140.

Meanwhile, the CPU 641 instructs the CMUT array 130 to detect thephotoacoustic wave in synchronization with the instruction to emit thelaser light at step S502. In this example, ultrasonic gel whose acousticimpedance is close to that of the breast 100 was provided as an acousticmatching medium between the CMUT array 130 and the breast 100.

Subsequently, at step S504, the FPGA 642 amplified the electric signaland performed A/D conversion thereof. The CPU 641 saved the signalamplified and subjected to the A/D conversion in the RAM 645 asphotoacoustic signal data.

Subsequently, at step S505, it was determined whether the measurement ofthe object was completed. When the measurement of the object iscompleted, the procedure shifts to step S506. When the measurement ofthe object is not completed, the procedure shifts to step S502. In thisexample, since the number of irradiation times of the laser light wasset to 30 at step S501, the measurement is completed when the procedurefrom step S502 to step S504 is repeated 30 times.

A screen displayed on a liquid crystal display 160 as a display unitused in a following step is illustrated in FIG. 7. The user may select adesired item from an item 701 corresponding to BD processing, an item702 corresponding to UBP processing, an item 703 corresponding to MBPprocessing, and an item 704 corresponding to CF processing.

The items 701 to 704 corresponding to each processing and progress bars711 to 714 indicating a progress situation of each processing aredisplayed next to one another. When a black bar of each of the progressbars 711 to 714 is located on a left end, progress of the correspondingprocessing is indicated to be 0% and when this reaches a right end, theprogress of the corresponding processing is indicated to be 100%. Bythis configuration, the user may grasp the progress situation and timeremained of the corresponding processing from a position and a speed ofthe progress bar.

FIG. 7 illustrates the screen displayed when the item 701 correspondingto the BD processing is selected at step S508 to be described later andthe item 703 corresponding to the MBP processing is selected at stepS512 thereafter. At that time, the black bar of the progress bar 713corresponding the MBP processing does not reach the right end asillustrated in FIG. 7. Therefore, it is understood that the MBPprocessing is not finished at that time.

Subsequently, at step S506, the CPU 641 referred to the RAM 645 anddisplayed a list of pieces of the saved photoacoustic signal data in adata selection window 720. Then, the user selected one of the pieces ofphotoacoustic signal data displayed in the data selection window 720.

Meanwhile, in this example, an ID number of the subject andphotographing time of the photoacoustic signal data are displayed in thedata selection window 720 such that they may be selected.

Subsequently, at step S507, the CPU 641 read the measurement parametercorresponding to the photoacoustic signal data selected by the user atstep S506 and displayed the object information which may be displayed inan object information selection window 730. Then, the user selected theitem corresponding to initial sound pressure.

The initial sound pressure, an absorption coefficient, and oxygensaturation are displayed in the object information selection window 730.However, since it was measured by using only one wavelength 797 nm, theoxygen saturation being spectral characteristics cannot be selected inthis example. The initial sound pressure and the absorption coefficientwhich may be selected by the user and the oxygen saturation which cannotbe selected by the user are displayed in different colors.

Subsequently, at step S508, the CPU 641 determines whether the item 701corresponding to the BD processing is selected by the user. When theitem 701 corresponding to the BD processing is selected, the procedureshifts to step S509. When the item 701 corresponding to the BDprocessing is not selected, the procedure shifts to step S510.Meanwhile, since the user selects the item 701 corresponding to the BDprocessing, the procedure shifts to step S509 in this example.

Subsequently, at step S509, the CPU 641 read the photoacoustic signaldata selected by the user from the RAM 645 and applied theabove-described BD processing to the photoacoustic signal data. Then,the photoacoustic signal data to which the BD processing was applied wassaved in the RAM 645.

Subsequently, at step S510, the CPU 641 determined whether the item 702corresponding to the UBP processing was selected. When the item 702corresponding to the UBP processing is selected, the procedure shifts tostep S511. When the item 702 corresponding to the UBP processing is notselected, the procedure shifts to step S512. Since the user does notselect the item 702 corresponding to the UBP processing, the procedureshifts to step S512 in this example.

Subsequently, at step S512, the CPU 641 determined whether the item 703corresponding to the MBP processing was selected. When the item 703corresponding to the MBP processing is selected, the procedure shifts tostep S513. When the item 703 corresponding to the MBP processing is notselected, the procedure shifts to step S510. Meanwhile, since the userselects the item 703 corresponding to the MBP processing, the procedureshifts to S513 in this example.

Subsequently, at step S513, the CPU 641 instructed the GPU 643 toperform the MBP processing. Then, the GPU 643 applied the MBP processingto the photoacoustic signal data to which the BD processing was appliedat step S509 to generate three-dimensional voxel data related to theinitial sound pressure. The three-dimensional voxel data was saved inthe RAM 645.

Subsequently, at step S514, the CPU 641 determines whether the item 704corresponding to the CF processing is selected. When the item 704corresponding to the CF processing is selected, the procedure shifts tostep S515. When the item 704 corresponding to the CF processing is notselected, the procedure shifts to step S516. In this example, the userselects the item 704 corresponding to the CF processing, so that theprocedure shifts to step S515.

Subsequently, at step S515, the CPU 641 applied the CF processing to thethree-dimensional voxel data related to the initial sound pressurestored in the RAM 645 to generate the three-dimensional voxel datarelated to the initial sound pressure subjected to the CF processing.Then, the three-dimensional voxel data related to the initial soundpressure after being subjected to the CF processing was saved in the RAM645. By applying the CF processing at this step, resolution of thethree-dimensional voxel data related to the initial sound pressure wasimproved.

Subsequently, at step S516, the GPU 643 applied scan transformprocessing to the three-dimensional voxel data related to the initialsound pressure stored in the RAM 645 to generate display data. Then, theCPU 641 output the display data to the liquid crystal display 160 andinitial sound pressure distribution was displayed in an image displaywindow 740.

Subsequently, the procedure shifts to step S508 again to determinewhether the item corresponding to each processing is selected and whenany item is selected, the processing corresponding to the item isexecuted.

According to this example, the user may execute the desired processingto display the object information. Therefore, the user may diagnose byusing an image obtained by the processing meeting needs of the user suchas processing time and an image quality by using the photoacousticsignal data obtained at certain time.

Example 2

Subsequently, Example 2 of the present invention is described. Thisexample is different from Example 1 in that a plurality of types ofprocessing is started in parallel and desired processing may be selectedfrom finished processing.

In this example, an object information obtaining device illustrated inFIGS. 1 and 6 was used as in Example 1. Hereinafter, a method ofobtaining object information of this example is described with referenceto a flow illustrated in FIG. 8. Meanwhile, the flow illustrated in FIG.8 is executed by a computer 140.

In this example, a CPU 641 issued an instruction to a GPU 643 to executeUBP processing at step S511 to photoacoustic signal data to which BDprocessing was applied after steps up to step S509. Further, the CPU 641issued an instruction to the GPU 643 to execute MBP processing at stepS513 in parallel with step S511.

Meanwhile, reconstruction processing is stored in a ROM 644 as adifferent thread program. Each processing is executed by each of aplurality of processors assigned in the GPU 643.

A screen displayed on a liquid crystal display 160 at that time isillustrated in FIG. 9. When a progress bar 712 indicating progress ofthe UBP processing is confirmed, the progress is indicated to be 100%,so that initial sound pressure distribution corresponding to the UBPprocessing may be selected.

On the other hand, when a progress bar 713 indicating the progress ofthe MBP processing is confirmed, the progress is not indicated to be100%. Therefore, a user cannot select an item 703 corresponding to theMBP processing. This is because the MBP processing requires longerprocessing time than that of the UBP processing.

In this example, an item 702 corresponding to the UBP processing whichmay be selected is displayed with white background and the item 703corresponding to the MBP processing which cannot be selected isdisplayed with gray background, so that the user could visuallyrecognize whether the processing may be selected.

Subsequently, at step S510, the CPU 641 determined whether the item 702corresponding to the UBP processing was selected. When the item 702corresponding to the UBP processing is selected, the procedure shifts tostep S516. When the item 702 corresponding to the UBP processing is notselected, the procedure shifts to step S512. In this example, the userselects the item 702 corresponding to the UBP processing whichpreviously becomes selectable, so that the procedure shifts to stepS516.

Subsequently, the procedure shifts to step S510 again to determinewhether the item corresponding to each processing is selected, and whenany item is selected, the object information corresponding to the itemis displayed.

As described above, the number of finished processing increases withtime, so that the types of processing which the user may select alsoincrease with time in this example. Therefore, a diagnostic method ofconfirming the object information obtained in a short time by the UBPprocessing and the like first and confirming the object informationobtained by the MBP processing and the like when further detail isrequired during reading as in this example becomes possible.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiment(s) of the present invention, andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s). The computer may comprise one or more ofa central processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processing units. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

1. An image generating apparatus, comprising: a light source configuredto emit light; an acoustic wave detecting unit configured to detect aphotoacoustic wave generated in an object in response to irradiationwith the light and output an electric signal in response to detection ofthe acoustic wave; and an arithmetic unit configured to generatephotoacoustic signal data based on the electric signal and generateimage data based on the photoacoustic signal data, wherein thearithmetic unit is configured to: cause a display unit to display atleast any two of a plurality of candidates including a time-domain imagereconstruction processing, a Fourier-domain image reconstructionprocessing and a model base image reconstruction processing, those ofwhich are ready to be specified by a user; perform image reconstructionprocessing specified by the user on the photoacoustic signal dataconfigured to generate the image data; and cause the display unit todisplay an image based on the image data.
 2. The image generatingapparatus according to claim 1, wherein the arithmetic unit isconfigured to cause a display unit to display a plurality of candidatesincluding a time-domain image reconstruction processing, aFourier-domain image reconstruction processing and a model base imagereconstruction processing, those of which are ready to be specified by auser, wherein a processing time of the time-domain image reconstructionprocessing is shorter than a processing time of the model base imagereconstruction processing, and wherein a processing time of theFourier-domain image reconstruction processing is shorter than aprocessing time of the model base image reconstruction processing, andwherein a processing time of the Fourier-domain image reconstructionprocessing is shorter than a processing time of the model base imagereconstruction processing.
 3. The image generating apparatus accordingto claim 1, further comprising a storage unit configured to store thephotoacoustic signal data, wherein the arithmetic unit is configured togenerate the image data based on the photoacoustic signal data stored inthe storage unit.
 4. The image generating apparatus according to claim1, wherein, in a case where none of candidates in image reconstructionprocessing is specified by the user, the arithmetic unit is configuredto generate default image data by performing default imagereconstruction processing on the photoacoustic signal data, and causethe display unit to display a default image based on the default imagedata.
 5. The image generating apparatus according to claim 4, whereinthe arithmetic unit is configured to perform, before the imagereconstruction processing is specified by the user, a provisional imagereconstruction processing on the photoacoustic signal data, and wherein,when the provisional image reconstruction processing is in associationwith the image reconstruction processing specified by the user after theprovisional image reconstruction processing is completed, the arithmeticunit is configured to cause the display unit to display an image basedon an image data obtained by the provisional image reconstructionprocessing instead of displaying the default image.
 6. The imagegenerating apparatus according to claim 4, wherein a processing periodof time of the default image reconstruction processing is shorter than aprocessing period of time of the provisional image reconstructionprocessing.
 7. The image generating apparatus according to claim 4,wherein the default image reconstruction is time-domain imagereconstruction processing or Fourier-domain image reconstructionprocessing, the provisional image reconstruction is model base imagereconstruction processing, wherein a processing time of the time-domainimage reconstruction processing is shorter than a processing time of themodel base image reconstruction processing, and wherein a processingtime of the Fourier-domain image reconstruction processing is shorterthan a processing time of the model base image reconstructionprocessing.
 8. The image generating apparatus according to claim 7,wherein the arithmetic unit is configured to perform, before theprovisional image reconstruction processing is specified by the user,the provisional image reconstruction processing on the photoacousticsignal data, and wherein, when the provisional image reconstructionprocessing is specified by the user after the provisional imagereconstruction processing is completed, the arithmetic unit isconfigured to cause the display unit to display the image based on theimage data instead of displaying the default image.
 9. The imagegenerating apparatus according to claim 1, wherein the arithmetic unitis configured to cause the display unit to display items for specifyinga certain image reconstruction processing among the plurality ofcandidates in image reconstruction processing.
 10. The image generatingapparatus according to claim 9, wherein the arithmetic unit isconfigured to cause the display unit to display an item corresponding toimage reconstruction processing which is completed and an itemcorresponding to image reconstruction processing which is not completed,with a different color from each other.
 11. The image generatingapparatus according to claim 1, wherein the arithmetic unit isconfigured to cause the display unit to display information whichrepresents each progress of the default and provisional imagereconstruction processing.
 12. The image generating apparatus accordingto claim 1, wherein the arithmetic unit is configured to cause thedisplay unit to display information which represents each predictedcalculation termination time of the plurality of candidates in imagereconstruction processing.
 13. The image generating apparatus accordingto claim 1, wherein the arithmetic unit is configured to generate theimage data on any one of an initial sound pressure distribution, anoptical energy absorption density distribution, an absorptioncoefficient distribution, an oxygen saturation distribution, anoxy-hemoglobin density distribution, a deoxy-hemoglobin densitydistribution, and a total hemoglobin density distribution.
 14. The imagegenerating apparatus according to claim 1, wherein the arithmetic unitis configured to perform two or more types of image reconstructionprocessing including the default and provisional image reconstructionprocessing.
 15. A signal processing apparatus, comprising: an arithmeticunit configured to: obtain, from a storage unit, photoacoustic signaldata generated by detecting a photoacoustic wave generated in an objectin response to irradiation with light; show at least any two of aplurality of candidates including a time-domain image reconstructionprocessing, a Fourier-domain image reconstruction processing and a modelbase image reconstruction processing, those of which are ready to bespecified by a user, obtain information on a specified imagereconstruction processing which is specified by a user, to be performedon the photoacoustic signal data; generate image data by performingspecified image reconstruction processing; and cause a display unit todisplay an image based on the image data.
 16. An image generatingmethod, comprising: obtaining photoacoustic signal data generated bydetecting a photoacoustic wave generated in an object in response toirradiation with light, showing at least any two of a plurality ofcandidates including a time-domain image reconstruction processing, aFourier-domain image reconstruction processing and a model base imagereconstruction processing, those of which are ready to be specified by auser, obtaining information on a specified image reconstructionprocessing which is specified by a user, to be performed on thephotoacoustic signal data, generating image data by performing specifiedimage reconstruction processing, and causing a display unit to displayan image based on the image data.
 17. A non-transitory computer-readablerecording medium storing a program for executing the image generatingmethod according to claim 16.